Computing device with nfc and active load modulation

ABSTRACT

An RFID card includes a smartcard controller that receives power from a host device. The RFID card also includes a small inductive device capable of inductive coupling with an RFID reader. The small inductive device is small enough to fit in the form factor of a memory card or SIM card. Enhancement circuits enhance the usable read and write distance of the RFID card.

FIELD

The present invention relates generally to contactless communicationsdevices, and more specifically to contactless smartcard devices.

BACKGROUND

RFID “tags” can be separated into two broad categories: active tags andpassive tags. Active tags are characterized by a local power source suchas a battery. Active tags generally transmit information by broadcastingon an RF carrier frequency of choice using a locally generated RFcarrier. Active tags are typically used to transmit over long distances,often referred to as “far field communications” (FFC). Antennas usedwith active RFID tags tend to be large to allow for the communicationsover long distances.

Passive tags are not powered. Passive tags derive the energy needed topower the tag from an interrogating RF field, and use that energy totransmit response codes by modulating the impedance that the antennapresents to the interrogating field, thereby modulating the signalreflected back to the reader antenna. Passive tags are typically used totransmit over short distances, often referred to as “near fieldcommunications” (NFC). For example, passive tags operating at 13.56 MHzare typically designed to communicate with RFID readers a fewcentimeters away.

Passive tags are typically connected to “loop antennas.” One example ofa loop antenna is shown in U.S. Pat. No. 6,568,600, issued to Carpier etal. on May 27, 2003 (the '600 patent). The device described in the '600patent is recognizable as a “credit card sized” passive RFID card (morespecifically, a card that conforms to ISO 7816 size requirements). Theloop antenna is necessarily large because passive tags are powered usingenergy received by the antenna from signals transmitted by the RFIDreader.

FIG. 12 shows a power supply voltage developed over time by rectifying avoltage induced in a loop antenna in the presence of an interrogating RFfield. Once the power supply voltage reaches a critical value, the tagis powered up and can operate. As the antenna size is reduced, it takeslonger for the power supply voltage to reach the critical value, and thetag operation may not meet response time specifications. Below a certainantenna size, the power supply voltage may never reach the criticalvalue, and the tag may never power up.

Antenna design for RFID applications is described in a MicrochipTechnology, Inc. application note entitled “Antenna Circuit Design forRFID Applications” by Youbok Lee, Ph.D., published in 2003 (no monthgiven). Dr. Lee's application note describes in great detail how todetermine size requirements for a passive RFID tag antenna to operate at13.56 MHz. On page 5 of the application note, Dr. Lee shows that theoptimum radius of the loop antenna coil is equal to 1.414 times therequired read range. This analysis confirms that for a read range on theorder of a few centimeters, a credit card sized loop antenna can be madenear optimal.

Passive tags are seeing widespread use in many applications. Forexample, mobile device manufacturers are embedding passive RFID tags inmobile devices for NFC applications. Example mobile applicationsinclude, but are not limited to, ticketing and mobile payments. U.S.Pat. No. 7,333,062 issued to Leizerovich et al. on Feb. 19, 2008 (the'062 patent) shows a mobile phone with an integrated loop antenna for anNFC device. As shown in the '062 patent, the mobile phone provides thereal estate necessary to implement a loop antenna at 13.56 MHz.

There have been attempts to implement passive tags in smaller mobiledevices. These attempts have met with limited success due in part to thesize of the loop antenna. For example, FIG. 13 shows an RFID tagimplementation in a secure digital (SD) memory card manufactured byWireless Dynamics, Inc. of Calgary, Alberta Canada. Card 1300 includesan antenna, but the SD card is significantly oversized as a result. Alsofor example, U.S. Patent Application Publication No.: US 2006/0124755 A1shows a memory card having a passive tag, but the card must be insertedinto a slot to access a loop antenna on a different device. In thisimplementation, mobile device real estate is still relied upon for loopantenna implementation. It can be seen, therefore, that the size ofantennas are proving to be a barrier to further miniaturization ofpassive RFID tags.

FIG. 14 shows a prior art smartcard controller and antenna incombination. Smartcard controller 330 includes a contactless interfacethat includes two pads 1472 and 1474 intended for connection to a coil(antenna 1480). Smartcard controller 330 also includes bridge rectifier1420 to rectify an alternating voltage present on pads 1472 and 1474when antenna 1480 is inductively coupled to another device and in thepresence of an interrogating RF field. Capacitor 1440 is typically tunedto create a resonant circuit at the frequency of interest (e.g., 13.56MHz). When antenna 1480 is a large loop antenna, then bridge rectifier1420 provides power to internal circuits as shown in FIG. 12.Demodulator 1430 demodulates data present in the interrogating RF field,and load modulation driver circuit 1410 modulates an impedance seen bythe device presenting the interrogating RF field when the coil (antenna1480) is inductively coupled to a separate device that is presenting theinterrogating RF field. This creates a half-duplex communications pathbetween the device presenting the interrogating RF field and smartcardcontroller 330. Examples of smartcard controllers are the “SmartMX”controllers sold by NXP Semiconductors N.V. of Eindhoven, TheNetherlands.

A need exists for a small footprint RFID tag that does not rely on anexternal device to house an antenna. A need also exists for a memorycard compatible RFID tag that is compatible with standard memory cardslots on mobile devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a mobile computing device and a small RFID card compatiblewith a memory card slot;

FIG. 2 shows a block diagram of a mobile computing device;

FIGS. 3A-3B show block diagrams of memory card compatible RFID cardswith integrated inductive elements;

FIG. 4 shows a memory card compatible RFID card with an integratedinductive element;

FIG. 5 shows a data portion of a memory card write command;

FIG. 6-11 show flowcharts of methods in accordance with variousembodiments of the present invention;

FIG. 12 shows a power supply voltage developed over time by rectifying avoltage induced in a loop antenna in the presence of an interrogating RFfield;

FIG. 13 shows a prior art RFID tag implementation in a secure digital(SD) memory card;

FIG. 14 shows a prior art smartcard controller and antenna incombination;

FIG. 15 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and a single antennain accordance with various embodiments of the present invention;

FIG. 16 shows frequency spectrum used in RFID communications;

FIG. 17 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and separate receiveand transmit antennas in accordance with various embodiments of thepresent invention;

FIG. 18 shows frequency spectrum used in RFID communications;

FIG. 19 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and multipletransmit antennas in accordance with various embodiments of the presentinvention;

FIG. 20 shows frequency spectrum used in RFID communications;

FIG. 21 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and a singleantenna in accordance with various embodiments of the present invention;

FIG. 22 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and separatereceive and transmit antennas in accordance with various embodiments ofthe present invention;

FIG. 23 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and multipletransmit antennas in accordance with various embodiments of the presentinvention;

FIG. 24 shows a smartcard controller with a pad to provide digital dataoutput;

FIG. 25 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and a single antenna in accordance with various embodiments ofthe present invention;

FIG. 26 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and separate receive and transmit antennas in accordance withvarious embodiments of the present invention;

FIG. 27 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and multiple transmit antennas in accordance with variousembodiments of the present invention;

FIG. 28 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and a single antenna in accordance with various embodiments ofthe present invention;

FIG. 29 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and separate receive and transmit antennas in accordance withvarious embodiments of the present invention;

FIG. 30 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and multiple transmit antennas in accordance with variousembodiments of the present invention;

FIGS. 31-34 show performance enhancing application specific integratedcircuits (ASICs) coupled to various smartcard controllers in accordancewith various embodiments of the present invention;

FIG. 35 shows a memory card with integrated smartcard controller,performance enhancement circuits and antennas in accordance with variousembodiments of the present invention;

FIG. 36 shows a memory card with integrated smartcard controller andperformance enhancement circuits in accordance with various embodimentsof the present invention;

FIG. 37 shows a subscriber identity module (SIM) card with integratedsmartcard controller, performance enhancement circuits and antennas inaccordance with various embodiments of the present invention;

FIG. 38 shows a subscriber identity module (SIM) card with integratedsmartcard controller and performance enhancement circuits in accordancewith various embodiments of the present invention; and

FIG. 39 shows a mobile device with a smartcard controller, enhancementcircuits, and antenna(s).

DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, variousembodiments of an invention. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. It is to be understood that the various embodiments of theinvention, although different, are not necessarily mutually exclusive.For example, a particular feature, structure, or characteristicdescribed in connection with one embodiment may be implemented withinother embodiments without departing from the spirit and scope of theinvention. In addition, it is to be understood that the location orarrangement of individual elements within each disclosed embodiment maybe modified without departing from the spirit and scope of theinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined only by the appended claims, appropriately interpreted, alongwith the full range of equivalents to which the claims are entitled. Inthe drawings, like numerals refer to the same or similar functionalitythroughout the several views.

FIG. 1 shows a mobile computing device and a small RFID card compatiblewith a memory card slot. Mobile computing device 110 is shown as amobile phone in FIG. 1, but this is not a limitation of the presentinvention. For example, mobile computing device 110 may be a personaldigital assistant (PDA), a smartphone, a mobile phone, a handheldcomputer, a desktop computer, or any other device capable of operatingas described herein.

Mobile computing device 110 includes memory card slot 112. Memory cardslot 112 is a slot capable of accepting RFID card 120. For example,memory card slot 112 may have physical dimensions compatible with RFIDcard 120, and may have a communications interface that operates using aprotocol compatible with RFID card 120. In some embodiments of thepresent invention, memory card slot 112 is a memory card slot designedto accept and communicate with memory cards. As used herein, the term“memory card slot” refers to any add-on slot capable of accepting a cardhaving memory accessible by a mobile computing device such as that shownin FIG. 1. For example, a memory card slot may be compatible with anindustry standard communications protocol, or may be compatible with awidely accepted communications protocol that is not necessarily formallydocumented as an industry standard. Examples include slots that arecompatible with the Multimedia Memory Card (MMC) protocol, Memory StickDUO protocol, secure digital (SD) protocol, and Smart Media protocol.The foregoing list is meant to be exemplary, and not exhaustive. Memorycard slot 112 may be compatible with many memory card slot protocolsother than those explicitly listed above without departing from thescope of the invention. Further, in some embodiments, memory card slot112 accepts a subscriber identity module (SIM) card. Memory card slot112 may be exposed on an edge of mobile computing device 110 as shown,or may be behind a cover. For example, memory card slot 112 may bebehind a battery cover, behind a battery, or anywhere else on mobilecomputing device 110.

RFID card 120 includes electrical contacts 122 as part of a hostinterface that communicates with memory card slot 112. For example,electrical contacts 122 may provide connectivity compliant with acommunications protocol for memory cards. RFID card 120 includes RFIDfunctionality, and may also include memory accessible by mobilecomputing device 110. For example, in some embodiments, RFID card 120includes a smartcard controller and an inductive element capable ofinteracting with an NFC reader (e.g., an ISO 14443 compliant interface).In other embodiments, RFID card 120 does not include memory accessibleby mobile computing device 110. RFID card 120 may include functionalitybeyond memory and RFID. Electrical contacts 122 may also be compliantwith a smartcard “contact” interface (e.g., ISO 7816).

In various embodiments of the present invention, the RFID functionalityin RFID card 120 is accessed by mobile computing device 110 using memorycard access commands already defined for use in memory card slot 112.Accordingly, the various embodiments of the present invention enable theimplementation of RFID functions beyond memory accesses without definingnew commands. In some embodiments, new commands for the RFID card areembedded inside the data bits subsequent to memory card read/writecommands. RFID card 120 then decides if the incoming data bits are meantfor regular read/write memory functions or for RFID functions. In otherwords, functions in addition to standard memory card functions may beaccessed through commands “hidden” in the data stream that can beexchanged using existing memory card access commands and functions.According to the various embodiments of the invention, both existingmemory card functions and RFID functions may be implemented withoutrequiring changes in how the host protocol is built.

The combination of mobile computing device 110 and RFID card 120 may beused for any purpose. For example, in some embodiments, RFID card 120may interact with a point-of-sale payment device to effect mobilepayments. Also for example, in some embodiments, RFID card 120 may beused in wave-and-pay ticketing in mass transit environments, such asMIFARE.

FIG. 2 shows a block diagram of a mobile computing device. Mobilecomputing device 110 includes antenna 240, radio circuits 230, processor210, memory 220, and memory card slot 112. In some embodiments, mobilecomputing device 110 is a mobile phone, or includes mobile phonefunctionality. For example, antenna 240 and radio circuits 230 may beutilized to communicate with a cellular telephone network. Further, insome embodiments, mobile computing device 110 is a wireless local areanetwork (WLAN) or wireless wide area network (WWAN) device. For example,antenna 240 and radio circuits 230 may be utilized to communicate with awireless access point. In some embodiments, antenna 240 and radiocircuits 230 are omitted, and mobile computing device 110 does notutilize wireless connectivity.

Processor 210 represents a processor capable of communicating with theother blocks shown in mobile computing device 110. For example,processor 210 may be a microprocessor, a digital signal processor (DSP),a microcontroller, or the like. Further, processor 210 may be formedfrom state machines or other sequential logic. In operation, processor210 may read instructions from memory 220 and perform actions inresponse thereto. For example, processor 210 may execute programinstructions that influence communications between mobile computingdevice 110 and a device coupled to memory card slot 112.

Memory card slot 112 is described above with reference to FIG. 1. Memorycard slot 112 includes circuitry compatible with RFID card 120. Mobilecomputing device 110 may communicate with RFID card 120 by using astandard set of memory card access commands. For example, processor 210may use memory card write commands to write to memory in RFID card 120,and may use memory card read commands to read from memory in RFID card120. Mobile computing device 110 may also communicate with RFID card 120using a ISO 7816 compatible interface or the like. For example, whenRFID card 120 is a SIM card, mobile computing device 110 may communicatewith a smartcard controller within the SIM card.

Mobile computing device 110 may access the RFID functionality in RFIDcard 120 using “hidden” commands embedded in memory card accesscommands. For example, a memory card write command may include a uniquedata string to identify the memory card write command as a command to bediverted for purposes other than a memory write. In addition, the sectoraddress provided with the memory card write command may be set to aparticular address value to further identify the memory card writecommand as a command to be diverted. In addition to specificaddress/data values to identify the memory card access command as acommand to be diverted for a purpose other than a memory access, thememory access command may include data bits to further specify the typeand function of hidden command. Example formats of hidden commands aredescribed further below. In some embodiments, a read command is issuedright after a write command to enable data flow from the non-memory cardfunctions to the host, where the write command's data had the hiddencommands. The combination of a memory card write command and a memorycard read command can be used in this manner to form a hidden readcommand.

In some embodiments, memory card slot 112 is powered down after periodsof inactivity to save power. For example, memory card slot 112 may bepowered up when processor 210 issues a memory card write or readcommand, but may then be powered down to save power. When memory cardslot 112 is powered down, any device coupled to the memory card slot isalso powered down. For example, if RFID card 120 (FIG. 1) is coupled tothe memory card slot, then RFID card 120 is powered down when memorycard slot 112 is powered down.

In various embodiments of the present invention, processor 210 executessoftware resident in memory 220 to maintain power to memory card slot112 (and to RFID card 120). For example, periodic hidden commands may besent to RFID card 120 for the purpose of keeping power applied whileRFID card 120 is expected to be providing RFID functionality. Also forexample, a hidden command may be sent to RFID card 120 for the purposeof cycling power to a smartcard controller resident on the card. Thesehidden commands are described further below with respect to laterfigures.

FIG. 3A shows a block diagram of a memory card compatible RFID card withan integrated inductive element. RFID card 300 represents possibleembodiments of RFID card 120 (FIG. 1). RFID card 300 includes hostinterface 310, memory card controller 340, memory 360, smartcardcontroller 340, program memory 332, and small inductive element 350.RFID card 300 is capable of communicating with a memory card slot in amobile computing device. Further, RFID card 300 does not require memorycard slots to implement extended input/output functions. For example,and not by way of limitation, in SD and micro SD embodiments, RFID card300 is operable in any SD or microSD memory card slot, and does notrequire a secure digital input output (SDIO) memory card slot.

Host interface 310 includes electrical contacts to interface with amemory card slot. For example, host interface 310 includes contacts suchas contacts 122 (FIG. 1). Also for example, in some embodiments, hostinterface 310 includes recessed electrical contacts. Host interface 310may also include circuitry such as drivers, receivers, terminations, andthe like.

In embodiments represented by FIG. 3A, memory card controller 340communicates with the mobile device using memory card access commands.Memory card controller 340 also communicates with memory 360. Memorycard controller 340 determines whether each command should result in amemory operation with memory 360, whether a hidden command should bediverted to smartcard controller 330, or whether memory card controller340 should take action in response to a hidden command. In someembodiments, memory card controller 340 executes instructions that arestored in an internal memory or stored in memory 360. In someembodiments, memory card controller 340 includes special purposehardware useful to determine whether a command should be diverted. Inother embodiments, memory card controller 340 may be a microcontrolleridentical in all respects to a controller found in memory cards, exceptfor the program that it executes.

Memory 360 may be any type of volatile or non-volatile memory. Forexample, memory 360 may be volatile memory such as static random accessmemory (SRAM) or dynamic random access memory (DRAM). Also for example,memory 360 may be nonvolatile memory such as NOR FLASH memory or NANDFLASH memory. In various embodiments of the present invention, memory360 represents memory that is accessed by a mobile computing deviceusing memory card access commands defined for that purpose.

When RFID card 300 is communicating with a memory card slot in a mobilecomputing device, the mobile computing device may send a memory cardaccess command in order to access memory 360. Also for example, themobile computing device may send a memory card access command thatcontains a hidden command. Memory card controller 340 detects thepresence of the hidden command, and diverts all or a portion of thememory access command to smartcard controller 330 using communicationbus 342. Communication bus 342 may have any number of conductors and maytake any form. For example, communication bus 342 may be a serial port,a parallel port, or may include multiple data conductors, multipleaddress conductors, and/or conductors to carry control signals such asclock signals. In some embodiments, memory card controller 340 takes oneor more actions in response to a hidden command. For example, memorycard controller 340 may modify clock signals in response to a hiddencommand.

Memory card controller 340 can detect the hidden command in many ways.For example, in some embodiments, the memory card access command mayinclude a specific address value or a specific data value. Memory cardcontroller 340 detects commands that include one or both of the specificaddress value or specific data value and routes the commandappropriately. The specific address value and specific data value usedfor this purpose are referred to herein as the hidden command addressvalue and the hidden command data value.

In some embodiments, memory card controller 340 detects the presence ofhidden commands based only on the hidden command address value. In theseembodiments, memory card controller 340 checks the address valueincluded in a memory card access command, and diverts the command (ortakes some other action) if it matches the hidden command address value.In some embodiments, memory card controller 340 detects the presence ofhidden commands based only on the hidden command data value. In theseembodiments, memory card controller 340 checks a data value included inthe memory card access command, and diverts all or a portion of thecommand if it matches the hidden command data value. In still furtherembodiments, memory card controller 340 detects the presence of hiddencommands based on both the hidden command address value and the hiddencommand data value. In these embodiments, memory card controller 340diverts the command only if both the memory card access address and datamatch the hidden command address value and data value, respectively.

The hidden command address value and hidden command data value may bespecified in many ways. For example, all RFID cards may be issued withfixed values. In these embodiments, each time the RFID functions areaccessed, the same hidden command address and/or data value is includedin the memory card access command. Also for example, different RFIDcards may be issued with unique values. In these embodiments, each RFIDcard may provide these values to a mobile computing device when queried.Also for example, hidden command address and/or data values may bespecified by the mobile computing device. In still further embodiments,hidden command address and data values may be dynamic. The hiddencommand address and data values may change each time power is applied oron a periodic basis.

Smartcard controller 330 receives hidden commands diverted by memorycard controller 340. Smartcard controller 330 further interprets thehidden commands and performs actions in response thereto. Smartcardcontroller 330 executes instructions stored in program memory 332. Insome embodiments, program memory 332 is embedded in smartcard controller330, and in other embodiments, program memory 332 is part of memory 360.

Smartcard controller 330 is a dual interface smartcard controller withone of the interfaces including RFID functionality. In some embodiments,smartcard controller 330 is compatible with passive RFID tag readers inNFC applications. For example, smartcard controller 330 may be a devicecapable of implementing all or part of the ISO 14443 standard forcontactless NFC devices. Also for example, smartcard controller 330 maybe a dual interface smartcard controller capable of implementing bothISO 7816 and ISO 14443 standards for contact/contactless requirements.The “SmartMX” family of controllers available from NXP SemiconductorsN.V. of The Netherlands are examples of suitable dual interfacesmartcard controllers. These controllers provide RFID functionality at13.56 MHz. The various embodiments of the present invention operate at13.56 MHz, but are not limited to operation at this frequency. In someembodiments, smartcard controller interoperates with MIFARE systems forticketing applications.

Smartcard controller 330 receives power from the host interface. By notreceiving power from the interrogating RF field, the necessity of a loopantenna for power generation is negated. Smartcard controller 330includes a contactless interface that in turn includes antenna port 334.Antenna port 334 includes at least two pads for connection to anantenna, shown as 1742 and 1744 in FIG. 14 and later figures. In FIG.3A, antenna port 334 is coupled to small inductive element 350.

Small inductive element 350 includes a coil wound around a magneticcore. As described with reference to later figures, small inductiveelement may include one or more coils or antennas. The coil of smallinductive element is too small to draw power from the interrogating RFfield, but this is not necessary since smartcard controller 330 ispowered by the host device through host interface 310. Small inductiveelement 350 interacts with an antenna in an RFID reader similar to theway that primary and secondary coils in a transformer interact. The RFIDreader has a coil resonant at 13.56 MHz functioning as the primary coilof a transformer. Small inductive element 350 functions as the secondarycoil of the transformer. Accordingly, the transmitter “sees” theimpedance of the secondary coil (small inductive element 350). Smartcardcontroller 330 is able to modulate reflected RF signals using circuitryto modify the impedance at the antenna port 334.

Small inductive element 350 can be made very small. For example, in someembodiments, RFID card 120 is a miniSD card, microSD card, or SIM card,and small inductive element 350 is small enough to be completelycontained in the miniSD, microSD, or SIM form factor. A specificembodiment of a small inductive element in a memory card form factor isdescribed below with reference to FIG. 4.

In various embodiments of the invention, memory card controller 340 andsmartcard controller 330 are implemented in many different ways. Forexample, in some embodiments, the various components are implemented inhardware. In these embodiments, the various components may beimplemented as separate integrated circuits, or in a combined integratedcircuit. Also for example, in some embodiments, the various componentsmay be implemented in software, or in a combination of hardware andsoftware. In some embodiments, RFID card 300 may include amicroprocessor, and the components may be implemented as softwaremodules running on the microprocessor. In other embodiments, RFID card300 may include multiple processors, and the components may beimplemented as software modules distributed across the multipleprocessors.

FIG. 3B shows a block diagram of a memory card compatible RFID card withan integrated inductive element. RFID card 302 represents possibleembodiments of RFID card 120 (FIG. 1). RFID card 302 includes hostinterface 310, memory card controller 340, memory 360, smartcardcontroller 340, program memory 332, and small inductive element 350, allof which are described above with reference to FIG. 3A. RFID card 302 iscapable of communicating with a memory card slot in a mobile computingdevice. Further, RFID card 302 does not require memory card slots toimplement extended input/output functions. For example, and not by wayof limitation, in SD and microSD embodiments, RFID card 302 is operablein any SD or microSD memory card slot, and does not require a securedigital input output (SDIO) memory card slot.

In embodiments represented by FIG. 3B, smartcard controller 330 receivespower from memory controller 340. In these embodiments, memorycontroller 340 has direct control over the power provided to smartcardcontroller 330. Memory controller 340 may apply and/or remove power fromsmartcard controller 330 in response to commands received over the hostinterface. For example, memory controller 340 may receive a hiddencommand to reset smartcard controller 330 by causing a reboot through apower cycle.

FIG. 4 shows a memory card compatible RFID card with an integratedinductive element. RFID card 120 is shown in an SD card form factor,although this is not a limitation of the present invention. For example,other form factors within the scope of the present invention include,but are not limited to, microSD form factors and SIM card form factors.RFID card 120 includes electrical contacts 122, memory card controller340, smartcard controller 330, memory 360, magnetic core 450, and coil452, all affixed to circuit board 402.

Magnetic core 450 and coil 452 implement small inductive element 350(FIGS. 3A, 3B). As can be seen in FIG. 4, the small inductive elementfits entirely within the memory card form factor. The small inductiveelement does not provide power generation for smartcard controller 330,and so does not need to be made large for that purpose.

FIG. 5 shows a data portion of a memory card write command. Included arehidden command data value 510, status field 520, password field 530,device ID 532, command index 540, and hidden command related data 550.In the example of FIG. 5, the data portion is 512 bytes in length,although this is not a limitation of the present invention. Any amountof data may be included in the write command, and each field shown inFIG. 5 may be any length.

In the example of FIG. 5, the hidden command data value is 256 bitslong, although any length may be used without departing from the scopeof the present invention. In some embodiments, hidden command data value510 is used to identify a memory write command as a hidden command. Whena write command is received having data in the first 256 bits that matchthe hidden command data value, the command is identified as one to bediverted to the smartcard controller. As described above, a hiddencommand address value may be used in conjunction with, or instead of, ahidden command data value to identify the memory write command as ahidden command.

The remaining fields have significance when the memory write is a hiddencommand. For example, if the first 256 bits do not match the hiddencommand data value (or if the write address does not match the hiddencommand address value, or both) then the remaining bits in the datafield are to be treated as data in a normal memory write command. Incontrast, when the memory write is a hidden command, the remainingfields are used to further interpret the hidden command.

Memory card controller 340 (FIGS. 3, 4) inspect the hidden command datavalue 510, status field 520, and possibly password field 530 and deviceID 532. In some embodiments, if the command is identified as a hiddencommand, memory card controller 340 forwards the password 530, commandindex 540, and related data 550 to smartcard controller 330. In otherembodiments, memory card controller 340 may directly take actions basedon the hidden command.

Status field 520 may include any information relating to the status ofthe hidden command. For example, status field 520 may include one morebits to signify to memory card controller 340 whether the host (mobilecomputing device) is expecting the smartcard controller to return datain response to the hidden command. For example, when status field 520signifies a write, memory card controller 340 forwards the password,device ID, command index, and related data without expecting to returnany data to the host. Also for example, when status field 520 signifiesa read, memory card controller 340 forwards the password, device ID,command index, and related data with the expectation that smartcardcontroller 330 will provide data to be sent to the host in response to amemory card read command. The combination of a memory card write commandfollowed shortly thereafter by a memory card read command may be used toprovide “read” functionality to the smartcard controller. Readoperations from the smartcard controller are described further belowwith reference to FIG. 8.

Password field 530 includes a password to allow smartcard controller 330to authenticate the host to the RFID card. In some embodiments, everyhidden command includes a password. Each time the password, device ID,command index, and related data is diverted to the smartcard controller,the password is checked to authenticate the host to the RFID card.

Device ID 532 uniquely identifies the host (mobile computing device).The device ID may be checked by the smartcard controller to ensure thatthe RFID card is inserted in the host to which it is authenticated. Someembodiments of the present invention enforce a unique host/card pairingusing the device ID, and other embodiments allow smartcard controllerfunctions to be accessed by any host.

Command index 540 identifies the type of hidden command. The number ofpossible hidden commands is limited only by the number of bits allocatedthereto. Any number of bits may be allocated to command index 540without departing from the scope of the present invention. Hiddencommand related data 550 may be utilized differently for each type ofhidden command. Any number of bits may be used for hidden commandrelated data 550.

The data shown in FIG. 5 is provided as an example, and the data fieldof a memory card access command may include more or fewer data fieldsthan those shown in FIG. 5. The present invention is not limited by thenumber or content of the fields in a memory card access command.

FIG. 6 shows a flowchart in accordance with various embodiments of thepresent invention. In some embodiments, method 600 may be used by amobile computing device to communicate with an RFID card in a memorycard slot. In some embodiments, method 600, or portions thereof, isperformed by a mobile computing device with a memory card slot, and inother embodiments, method 600, or portions thereof, is performed bysoftware. The various actions in method 600 may be performed in theorder presented, in a different order, or simultaneously. Further, insome embodiments, some actions listed in FIG. 6 are omitted from method600.

Method 600 begins at 610 in which a data pattern and an address valueare received from an RFID card in a memory card slot. The data patterncorresponds to the hidden command data value, and the address valuecorresponds to the hidden command address value. In some embodiments,the mobile device only receives the data value and in other embodiments,the mobile device only receives the address value. In some embodiments,the actions of 610 may occur once when the RFID card is first insertedin the memory card slot. The mobile computing device may then use theaddress and data values each time it creates a hidden command. In otherembodiments, the actions of 610 may occur each time the RFID card isinserted in the memory slot. In still further embodiments, the actionsof 610 may occur periodically. Each time the actions 610 occur, the datapattern may be the same or different, and the address value may be thesame or different.

At 620, a data field of a memory card access command is populated withthe data pattern to cause the command to be diverted to a smartcardcontroller on the RFID card. For example, the data pattern may bewritten to the data field as the hidden command data value 510 (FIG. 5).

At 630, an address field of the memory card access command is populatedwith the address value to further cause the command to be diverted tothe smartcard controller. In some embodiments, only one of 620 or 630 isutilized. In these embodiments, the presence of a hidden command issignified by the data pattern alone, or the address value alone.

At 640, the data field of the memory card access command is populatedwith a command string to specify a purpose other than a memory cardaccess. For example, the command string may be written to the data fieldas the command index 540 for the smart card controller. This command maybe used for any purpose. For example, one or more hidden commands mayhave as a sole purpose keeping power provided to the memory card slot sothat the RFID card continues to receive power.

At 650, the data field of a memory card access command is populated witha password to authenticate access to the RFID card coupled to the memorycard slot. In some embodiments, a password is included in the data fieldfor every hidden command. In other embodiments, a password is onlyincluded at the beginning of an exchange.

At 660, the memory card access command is sent to the RFID card coupledto the memory card slot. For example, a mobile computing device (110,FIGS. 1, 2) may send the memory card access command to an RFID card(120, FIGS. 1, 3, 4) in a memory card slot (112, FIGS. 1, 2). The RFIDcard includes a memory card controller (340, FIG. 3) to divert thecommand (or take some other action) based on the data fields populatedin method 600.

FIG. 7 shows a flowchart in accordance with various embodiments of thepresent invention. In some embodiments, method 700 may be used by anRFID card in a memory card slot. In some embodiments, method 700, orportions thereof, is performed by a memory card controller within amemory card compatible RFID card, and in other embodiments, method 700,or portions thereof, is performed by software. The various actions inmethod 700 may be performed in the order presented, in a differentorder, or simultaneously. Further, in some embodiments, some actionslisted in FIG. 7 are omitted from method 700.

Method 700 begins at 710 in which a memory card access command isreceived from a mobile computing device via a host interface. Theactions of 710 correspond to an RFID card in a memory card slot of amobile computing device receiving a memory card access command.

At 720, the memory card controller checks criteria in the memory cardaccess command to determine if the memory card access command should bediverted to a smartcard controller resident on the RFID card. Thecriteria may be one or both of a hidden command data value, a hiddencommand address value, or both. If there is a criteria match at 730,then a hidden command is present, and at least a portion of the memorycard access command is diverted at 740. If there is not a criteriamatch, then no hidden command is present, and a memory access isperformed at 750.

FIG. 8 shows a flowchart in accordance with various embodiments of thepresent invention. In some embodiments, method 800 may be used by anRFID card in a memory card slot. In some embodiments, method 800, orportions thereof, is performed by a memory card controller within anRFID card, and in other embodiments, method 800, or portions thereof, isperformed by software. The various actions in method 800 may beperformed in the order presented, in a different order, orsimultaneously. Further, in some embodiments, some actions listed inFIG. 8 are omitted from method 800.

Method 800 begins at 810 in which a memory card write command isreceived from a mobile computing device via a host interface. If thememory card write command is determined to be a hidden command,processing continues with 840; otherwise, a memory write is performed at830.

At 840, the hidden command is diverted to a smartcard controller. Insome embodiments, this corresponds to sending command index 540 andhidden command related data 550 (FIG. 5) to the smartcard controller. Ifthe hidden command is determined to be a “read” at 850, processingcontinues at 860; otherwise, the hidden command processing is done. At860, the memory card controller retrieves non-memory data from thesmartcard controller, and at 870, a memory card read command is receivedfrom the mobile computing device. At 880, the non-memory data isreturned to the mobile computing device.

Method 800 demonstrates how a mobile computing device can perform a readfrom a smartcard controller in a memory card compatible RFID card. Themobile computing device issues a memory card write command with a hiddencommand having a status field designating a read, and then the mobilecomputing device issues a memory card read command. The processing inthe card receives the hidden command, identifies it as a read, and thenreturns data to the mobile computing device in response to a subsequentmemory card read command.

FIG. 9 shows a flowchart in accordance with various embodiments of thepresent invention. In some embodiments, method 900 may be used by anRFID card in a memory card slot. In some embodiments, method 900, orportions thereof, is performed by a smartcard controller within an RFIDcard, and in other embodiments, method 900, or portions thereof, isperformed by software. The various actions in method 900 may beperformed in the order presented, in a different order, orsimultaneously. Further, in some embodiments, some actions listed inFIG. 9 are omitted from method 900.

Method 900 begins at 910 in which a smartcard controller receives acommand from the memory card controller. This command corresponds to ahidden command received by the memory card controller. At 950, thesmartcard controller determines whether the command is a “dummy” commandused solely for the purpose of maintaining power to the memory cardslot. If no, then the smartcard function specified in the command isperformed at 930. If yes, then the command is disregarded at 960.

Method 900 allows a memory card compatible RFID card in a memory cardslot to remain powered during periods when the memory card slot in thehost device would otherwise remove power to save energy. This is acoordinated effort between software building hidden commands in a memorycard access command, the memory card controller diverting the hiddencommand to the smartcard controller, and the smartcard controllerdisregarding the command. According to embodiments represented by FIG.3A, providing power to the RFID card also provides power the smartcardcontroller, thereby allowing the use of a small inductive device such asthose shown in FIGS. 3 and 4.

FIG. 10 shows a flowchart in accordance with various embodiments of thepresent invention. In some embodiments, method 1000 may be used by anRFID card in a memory card slot. In some embodiments, method 1000, orportions thereof, is performed by a memory card controller within anRFID card, and in other embodiments, method 1000, or portions thereof,is performed by software. The various actions in method 1000 may beperformed in the order presented, in a different order, orsimultaneously. Further, in some embodiments, some actions listed inFIG. 10 are omitted from method 1000.

Method 1000 begins at 1010 in which a memory card controller receives ahidden command from a mobile computing device. If at 1020, the memorycard controller determines that the hidden command is to be diverted tothe smartcard controller, then the command is diverted at 1030. In someembodiments, this corresponds to sending command index 540 and hiddencommand related data 550 (FIG. 5) to the smartcard controller. If thecommand is not to be diverted, then the memory card controller does notdivert the command; however, the memory card controller may take otheractions at 1040 based on the hidden command. For example, the memorycard controller may modify a clock signal provided to the smartcardcontroller. Also for example, the memory card controller may assert areset signal to the smartcard controller. Still for example, the memorycard controller may cycle power to the smartcard controller. The memorycard controller is able to cycle power to the smartcard controller inembodiments represented by FIG. 3B.

Cycling power to the smartcard controller may be a coordinated effortbetween the hosting computing device and the memory card controller inthe RFID card. For example, power to the memory card slot may bemaintained by supplying dummy hidden commands to the RFID card asdescribed above with reference to FIG. 9. While power is maintained tothe memory card slot, hidden commands may be used to cause the memorycard controller to cycle power to the smartcard controller.

FIG. 11 shows a method authenticating a mobile computing device to oneor more functions in a memory card compatible RFID card. Method 1100begins at block 1110 in which an activation code is received at an RFIDcard from a mobile computing device. At 1120, the received activationcode is compared to a code stored in the RFID card. If the activationcode matches, the RFID card receives a password from the mobilecomputing device at 1140, and stores the password in the RFID card forlater use at 1150. If the activation code does not match, the RFID carddetermines whether a number of allowable tries has been exceeded at1160. If the number of allowable tries has been exceeded, the RFID cardissuer is contacted at 1170, and if the number of allowable tries hasnot been exceeded, the method repeats until either the activation codematches or the number of allowable tries has been exceeded.

Method 1100 may be performed when an RFID card is issued to a user. Forexample, the RFID card may be a mobile payment card issued by afinancial institution. The user may be provided an activation code to“activate” the RFID card. When the user successfully enters theactivation code, the user is prompted for a password, and that passwordis stored for use in future hidden commands.

In some embodiments, multiple non-memory functions in an RFID card areauthenticated using method 1100. For example, each of multiplenon-memory functions may have stored activation codes, and each isactivated separately. Each of the separately activated functions mayhave a different password, or the multiple functions may share apassword.

Embodiments described thus far include a power delivery mechanism fromthe host to the smartcard controller that allow the antenna or coil tobe very small. The small antenna or coil allows for higher levels ofintegration, but may also reduce the maximum distance at which the RFIDcard will function. For example, referring to FIG. 14, the voltageproduced by the antenna needs to overcome the diode drops of the bridgerectifier before data can be demodulated within the smartcardcontroller. As the antenna shrinks in size, the RFID card needs to becloser to the device producing the interrogating RF field in order toproduce a large enough voltage to overcome the bridge rectifier diodedrops, thereby reducing the maximum usable distance.

FIG. 15 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and a single antennain accordance with various embodiments of the present invention. Antenna1542 is a small inductive element as described above. Capacitor 1544 isin parallel with antenna 1542 and together they form tuned circuit 1540that is tuned to be resonant at the frequency of operation (e.g., 13.56MHz). The performance enhancement circuits include an amplifier 1510,outgoing data extraction circuit 1520, and load modulation drivercircuit 1530. Amplifier 1510 amplifies the voltage received at antenna1542, and the amplified voltage is provided to the smartcard controller.This increases the maximum distance at which the RFID card can operatewhile receiving data, but also creates a unidirectional data path wherea bidirectional data path previously existed. In other words, amplifier1510 forms a simplex communication path where a half duplex pathpreviously existed.

In order to restore the outgoing data path and re-create a half duplexcommunications system, the RFID card includes outgoing data extractioncircuit 1520 and load modulation driver circuits 1530. Outgoing dataextraction circuit 1520 receives a signal that is formed by theinterrogating RF field having been load modulated by the smartcardcontroller. For example, the impedance of the antenna port is modulatedby load modulation driver circuit 1410 (FIG. 14), where the modulatingsignal is the data. Outgoing data extraction circuit 1520 recovers thedata, and then load modulation driver circuit 1530 modulates theimpedance of the tuned circuit 1540 to form the outgoing data path.

Outgoing data extraction circuit 1520 may include one or more filters toextract the data. For example, referring now to FIG. 16, the loadmodulation driver circuit within the smartcard controller createsfrequency sidebands 1610 about the carrier frequency 1620 of theinterrogating RF field. Outgoing data extraction circuit 1520 mayinclude conventional filters to isolate one or more sidebands andextract the data. As shown in FIG. 16, in some 13.56 MHz embodiments,the bandwidth of the carrier frequency of the interrogating RF field maybe on the order of 850 KHz and the bandwidth of the sidebands may be onthe order of 100-200 KHz, although this is not a limitation of thepresent invention.

Load modulation driver circuit 1530 receives the extracted data fromoutgoing data extraction circuit 1520, and load modulates the tunedcircuit 1540 in response thereto. Load modulation driver circuits aregenerally well known, and may be as simple as a switched transistor thatadds and removes a reactive element from tuned circuit 1540. In someembodiments, load modulation driver circuit 1530 substantiallyduplicates the load modulation driver circuit 1410 within smartcardcontroller 330.

Amplifier 1510 is shown coupled to smartcard controller pad 1472, anddata extraction circuit 1520 is shown coupled to smartcard controllerpad 1474, but this is not a limitation of the present invention. Forexample, outgoing data extraction circuit 1520 may be coupled tosmartcard controller pad 1472 while amplifier 1510 may be coupled tosmartcard controller pad 1474. Also for example, both circuit 1520 andamplifier 1510 may be coupled to either pad 1472 or pad 1474 withoutdeparting from the scope of the present invention.

FIG. 17 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and separate receiveand transmit antennas in accordance with various embodiments of thepresent invention. FIG. 17 shows smartcard controller 330, amplifier1510, outgoing data extraction circuit 1520, and load modulation drivercircuit 1530, all of which are described above. FIG. 17 also shows tunedcircuits 1740 and 1750. Tuned circuit 1740 includes receive antenna 1742and capacitor 1744. Tuned circuit 1750 includes transmit antenna 1752and capacitor 1754. In some embodiments, receive antenna 1742 andtransmit antenna 1752 are small inductive elements as described above.

Separate transmit and receive antennas allow for different tuning, bothin frequency and bandwidth, or “Q.” For example, tuned circuit 1740 maybe tuned with relatively high Q for receive as shown at 1820 in FIG. 18,while tuned circuit 1750 may be tuned for a lower Q to envelope bothsidebands for transmit as shown at 1830 in FIG. 18. The higher Q tuningfor the receive antenna may further increase the maximum usable distancewhen the RFID card is receiving.

FIG. 19 shows a smartcard controller with performance enhancementcircuits including a load modulation driver circuit and multipletransmit antennas in accordance with various embodiments of the presentinvention. FIG. 19 shows smartcard controller 330, amplifier 1510,outgoing data extraction circuit 1520, load modulation driver circuit1530, and tuned receive circuit 1740, all of which are described above.FIG. 19 also shows two tuned transmit circuits 1950 and 1960. Tunedcircuit 1950 includes antenna 1952 and capacitor 1954, and tuned circuit1960 includes antenna 1962 and capacitor 1964. Antennas 1952 and 1962may be small inductive elements as described above.

Separate transmit antennas allow separate tuning for the two sidebands.For example, tuned circuit 1950 may be tuned for the lower sidebandtuned circuit 1960 may be tuned for the upper sideband as shown in FIG.20. Higher Q tuning of the transmit antennas for the separate sidebandsmay further increase the maximum usable distance when the RFID card istransmitting.

FIG. 21 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and a singleantenna in accordance with various embodiments of the present invention.The circuits shown in FIG. 21 are similar to FIG. 15 except the loadmodulation driver is replaced with an active transmit driver circuit2130. Active transmit driver circuit 2130 may include circuits toactively transmit a signal rather than simply load modulate tunedcircuit 1540. For example, active transmit driver circuit 2130 mayinclude one or more amplifiers filters, oscillators, modulators, etc.,to form a signal that mimics the sidebands 1610 (FIG. 16) as if theinterrogating RF field experienced load modulation. Active transmissioncan make use of power available on the RFID card and can furtherincrease the usable distance when smartcard controller 330 istransmitting.

FIG. 22 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and separatereceive and transmit antennas in accordance with various embodiments ofthe present invention. The circuits shown in FIG. 22 are similar to FIG.17 except the load modulation driver is replaced with an active transmitdriver circuit 2130. Active transmit driver circuit 2130 is describedabove with reference to FIG. 21.

FIG. 23 shows a smartcard controller with performance enhancementcircuits including an active transmit driver circuit and multipletransmit antennas in accordance with various embodiments of the presentinvention. The circuits shown in FIG. 23 are similar to FIG. 19 exceptthe load modulation driver is replaced with an active transmit drivercircuit 2130. Active transmit driver circuit 2130 is described abovewith reference to FIG. 21.

FIG. 24 shows a smartcard controller with a pad to provide a digitaldata output. Smartcard controller 2430 includes the antenna pads 1472and 1474 as described above. Smartcard controller 2430 also includes pad2410 which provides the digital data output directly. By providing thedigital data output directly, smartcard controller 2430 enables variousembodiments of the invention to eliminate the outgoing data extractioncircuit.

FIG. 25 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and a single antenna in accordance with various embodiments ofthe present invention. FIG. 25 shows smartcard controller 2430,amplifier 1510, load modulation driver circuits 1530, and tuned circuit1540, all of which are described above. Note that because smartcardcontroller 2430 provides digital data directly, the outgoing dataextraction circuit 1520 (FIG. 15) can be omitted, thereby reducing partscount and cost.

FIG. 26 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and separate receive and transmit antennas in accordance withvarious embodiments of the present invention. FIG. 26 shows circuitssimilar to those shown in FIG. 25, except that separate transmit andreceive antennas are provided. Separate transmit and receive antennas(and associated tuned circuits) allow for a higher Q tuning of thereceive antenna, thereby increasing the maximum usable distance whenRFID card is receiving. See FIG. 18.

FIG. 27 shows a smartcard controller with digital data output andperformance enhancement circuits including a load modulation drivercircuit and multiple transmit antennas in accordance with variousembodiments of the present invention. FIG. 27 shows circuits similar tothose shown in FIG. 26, except that multiple transmit antennas areprovided. Multiple separate transmit antennas (and associated tunedcircuits) allow for a higher Q tuning of each transmit antenna, therebyincreasing the maximum usable distance when RFID card is transmitting.See FIG. 20.

FIG. 28 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and a single antenna in accordance with various embodiments ofthe present invention. The circuits shown in FIG. 28 are similar to FIG.25 except the load modulation driver is replaced with an active transmitdriver circuit 2130. Active transmit driver circuit 2130 is describedabove with reference to FIG. 21. In general, the term “driver” as usedherein refers to an active transmit driver or a load modulation driveror any other method of driving the transmit output data.

FIG. 29 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and separate receive and transmit antennas in accordance withvarious embodiments of the present invention. The circuits shown in FIG.29 are similar to FIG. 26 except the load modulation driver is replacedwith an active transmit driver circuit 2130. Active transmit drivercircuit 2130 is described above with reference to FIG. 21.

FIG. 30 shows a smartcard controller with digital data output andperformance enhancement circuits including an active transmit drivercircuit and multiple transmit antennas in accordance with variousembodiments of the present invention. The circuits shown in FIG. 30 aresimilar to FIG. 27 except the load modulation driver is replaced with anactive transmit driver circuit 2130. Active transmit driver circuit 2130is described above with reference to FIG. 21.

FIGS. 31-34 show performance enhancing application specific integratedcircuits (ASICs) coupled to various smartcard controllers in accordancewith various embodiments of the present invention. FIGS. 31 and 32 showASICs coupled to smartcard controller 330. Both ASICs include amplifier1510 and outgoing data extraction circuits 1520. The ASIC of FIG. 31includes load modulation driver circuits 1530 and the ASIC of FIG. 32includes active transmit driver circuit 2130. FIGS. 33 and 34 show ASICscoupled to receive direct digital data from smartcard controller 2430.Accordingly, the outgoing data extraction circuits are omitted. The ASICof FIG. 33 includes amplifier 1510 and load modulation driver circuits1530, and the ASIC of FIG. 34 includes amplifier 1510 and activetransmit driver circuit 2130.

By combining a smartcard controller and an ASIC as described herein, theperformance of an RFID card may be enhanced with a reduced parts count.Further, any of ASICs shown may be used with separate receive andtransmit antennas, multiple transmit antennas, or any combination.Further, one ASIC may be provided with all of the functionality shown inFIGS. 31-34 and the manner in which it is connected to a smartcardcontroller will dictate which functional blocks (e.g., data extraction,load modulation, active transmit) are utilized.

FIG. 35 shows a memory card with integrated smartcard controller,performance enhancement circuits, and antennas in accordance withvarious embodiments of the present invention. Host interface 310, memorycard controller 340, and memory 360 are described above. Smartcardcontroller 3520 may be any smartcard controller described herein,including smartcard controller 330 or smartcard controller 2430.Enhancement circuits 3550 may include any of the enhancement circuitsdescribed herein including any combination of amplifier 1510, outgoingdata extraction circuits 1520, load modulation driver circuits 1530 andactive transmit driver circuit 2130. Antenna(s) 3560 may include anynumber or type of antennas. For example, antenna(s) 3560 may include oneantenna, separate transmit and receive antennas, or a receive antennaand multiple transmit antennas.

FIG. 36 shows a memory card with integrated smartcard controller andperformance enhancement circuits in accordance with various embodimentsof the present invention. The memory card of FIG. 36 shows circuitssimilar to FIG. 35 with the exception of antenna(s) 3560. Instead, thememory card of FIG. 36 is intended for use with a host device thatincludes antenna(s). In some embodiments, antenna(s) 3560 are includedin the memory card of FIG. 36, thereby allowing the host device todecide whether to use the antennas on the memory card, or the antennason the host device. The form factor of the memory card in FIGS. 35 and36 is shown as a microSD card, but this is not a limitation of thepresent invention. Any form factor may be employed.

FIG. 37 shows a subscriber identity module (SIM) card with integratedsmartcard controller, performance enhancement circuits and antennas inaccordance with various embodiments of the present invention. Smartcardcontroller 3520, enhancement circuits 3550, and antenna(s) 3560 aredescribed above with reference to FIG. 35.

FIG. 38 shows a subscriber identity module (SIM) card with integratedsmartcard controller and performance enhancement circuits in accordancewith various embodiments of the present invention. The SIM card of FIG.38 shows circuits similar to FIG. 37 with the exception of antenna(s)3560. Instead, the SIM ix) card of FIG. 38 is intended for use with ahost device that includes antenna(s). In some embodiments, antenna(s)3560 are included in the SIM card of FIG. 38, thereby allowing the hostdevice to decide whether to use the antennas on the SIM card, or theantennas on the host device.

FIG. 39 shows a mobile device with a smartcard controller, enhancementcircuits, and antenna(s). The mobile device of FIG. 39 includes abuilt-in smartcard controller for RFID functionality as opposed toaccepting a separate RFID card as described above. The mobile device maybe any electronic device including a mobile phone, a tablet computer, orthe like.

Although the present invention has been described in conjunction withcertain embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art readily understand.Such modifications and variations are considered to be within the scopeof the invention and the appended claims.

What is claimed is:
 1. A computing device comprising: a smartcardcontroller; an inductive element to interact with a near fieldcommunication (NFC) reader, wherein the inductive element is too smallto power the smartcard controller when placed in an interrogating radiofrequency field; and an active transmit driver coupled between thesmartcard controller and the inductive element to transmit digital data.2. The computing device of claim 1 wherein the smartcard controller iscoupled to receive power from the computing device.
 3. The computingdevice of claim 1 wherein the inductive element is tuned to be resonantat 13.56 MHz.
 4. The computing device of claim 3 wherein the smartcardcontroller is coupled to receive power from the computing device.
 5. Thecomputing device of claim 1 wherein the active transmit driver includesa load modulation driver circuit.
 6. The computing device of claim 1wherein interaction with an NFC reader effects mobile payments.
 7. Thecomputing device of claim 1 wherein the mobile device comprises a mobilephone.
 8. The computing device of claim 1 wherein the computing devicecomprises a mobile computing device.
 9. A computing device comprising: asmartcard controller; an inductive element to interact with a near fieldcommunication (NFC) reader, wherein the inductive element is too smallto power the smartcard controller when placed in an interrogating radiofrequency field; and a load modulation circuit coupled between thesmartcard controller and the inductive element to transmit digital data.10. The computing device of claim 9 wherein the smartcard controller iscoupled to receive power from the computing device.
 11. The computingdevice of claim 9 wherein the inductive element is tuned to be resonantat 13.56 MHz.
 12. The computing device of claim 9 wherein the smartcardcontroller is coupled to receive power from the computing device. 13.The computing device of claim 9 wherein interaction with an NFC readereffects mobile payments.
 14. The computing device of claim 9 wherein thecomputing device comprises a mobile phone.
 15. The computing device ofclaim 9 wherein the computing device comprises a mobile computingdevice.
 16. A computing device comprising: a smartcard controller; aninductive element to interact with a near field communication (NFC)reader, wherein the inductive element is too small to power thesmartcard controller when placed in an interrogating radio frequencyfield; and a performance enhancement circuit coupled between thesmartcard controller and the inductive element, the performanceenhancement integrated circuit including a load modulation drivercircuit to drive the inductive element.
 17. The computing device ofclaim 16 wherein the smartcard controller is coupled to receive powerfrom the computing device.
 18. The computing device of claim 16 whereinthe inductive element is tuned to be resonant at 13.56 MHz.
 19. Thecomputing device of claim 16 wherein interaction with an NFC readereffects mobile payments.
 20. The computing device of claim 16 whereinthe performance enhancement circuit further includes an amplifiercoupled to receive a signal from the inductive coil.